The present invention relates to a diaphragm valve, and particularly to a diaphragm valve that can be downsized.
As a diaphragm valve, there has been known one including a body provided with a fluid channel and a depression opening upward, a seat arranged in a circumferential edge of the fluid channel formed in the body, a spherical shell-shaped diaphragm that opens and closes the fluid channel by being pressed against and separated from the seat, a pressing adaptor that retains an outer circumferential edge portion of the diaphragm between a bottom surface of the depression of the body and itself, a diaphragm presser that presses a central portion of the diaphragm, and up and down movement means for moving up and down the diaphragm presser (Japanese Unexamined Patent Application Publication No. 05-80858 and the like).
In the above-described diaphragm, the outer circumferential edge portion thereof is fixed to the body, so that the depression opening upward provided in the body is sealed, and a central portion thereof can be elastically deformed (can move up and down) with respect to the outer circumferential edge portion. Thus, the diaphragm is elastically deformed with the up-to-down movement of the diaphragm presser to thereby contribute to fluid channel opening and closing.
Conventionally, a lower surface of the pressing adaptor is made up of a tapered portion having a predetermined inclination angle, and a flat portion provided in an outer circumference of a tapered surface, and an outer circumferential edge portion of the bottom surface of the depression of the body is circular and flat, so that the outer circumferential edge portion of the diaphragm is sandwiched between the flat portion of the pressing adaptor and the flat bottom surface of the outer circumferential edge portion of the body.
In the above-described conventional diaphragm valve, since the diaphragm is largely deformed every time opening and closing operations are performed, it is important to increase durability. Particularly, since when the diaphragm valve is downsized, the diaphragm is also downsized, the downsizing is disadvantageously difficult in view of durability assurance. In the conventional diaphragm valve, since the outer circumferential edge portion of the diaphragm is sandwiched between the flat portion of the pressing adaptor and the flat bottom surface of the outer circumferential edge portion of the body, the flat portion that cannot be deformed and is bent with respect to a spherical shell-shaped portion exists in the outer circumferential edge portion of the spherical shell-shaped and elastically deformable diaphragm, which brings a disadvantage in durability.